Actually, one of the complaints I have heard was that its much easier solo than with a party/crew due to difficulty scaling.
No. Difficulty does not scale with the number of involved players past one:
it remains the same as soon as two or more players are involved.
The difficulty is set on the same level for two, three or four players.
Running with a hunting party of three other players who know how to play and accept the gameplay terms is not more difficult.
It turns out way more difficult when players are unreliable and display the peculiar mindset: they do not like the game, they feel aggressed the game was not meant for them so they are going to spoil the game.
It is the same mindset exhibited when UgoIgo players go out for what is known a RT product and demand it to be UgoIgo.
Indeed, it is much more difficult to run with this kind of players than alone.
For example, lifes are pooled, a party can stack up to three deaths. Once it is reached, the hunt is over.
One player with the proper mindset, feeling the game is shit because it was not meant to match his tastes and the guy will keep dying to ruin the run.
There are other openings. That is why it might be the last MH that is true to the franchise. The devs are not that used to that kind of invasive, destructive mindset and will have to cope with it. It might end in transforming deeply the franchise.